Basically a particulate material is subject to physical and chemical influences which influence the resistance and the long-term suitability of the material. Thus in particular porous metal oxide particles, when acted upon by a pressure, have a tendency to instability of the particles and in particular when acted upon with aqueous solvent systems, particularly in the case of acid or basic systems, they have a tendency to rehydration of the metal oxide surface. The instability of the particles and the particle breakages resulting therefrom and also rehydration of the surface result in the particles forming lumps. Consequently the flow in a bulk mass of the particles is made more difficult and thus in the course of time blockages are caused in the bulk mass of particles, which make the bulk mass unusable.
In addition in processes in which separation of the particles is required, such separation of the fine particles which have been produced as a consequence of particle breakage is only possible using complicated and expensive technology, and the suspension effect makes re-use of the material almost impossible.
In principle there are demands in particular in regard to particle stability of the materials for a large number of applications and processes on a large technical scale such as for example Fischer-Tropsch processes, for example trans-esterification reactions, and also in chromatography.
In those processes the pore size and the distribution thereof on the one hand are also of significance in regard to stability and also reactivity and suitability in terms of process technology.
A large number of metal oxide materials for chemical and catalytic applications are known in the state of the art. Thus U.S. Pat. No. 4,422,960 discloses a particulate material for the hydrotreatment of a heavy hydrocarbon oil, wherein the material has a content of metal oxide comprising aluminium oxide, silicon dioxide, titanium dioxide, boron oxide, zirconium oxide, silicon dioxide-aluminium oxide, silicon dioxide-magnesium oxide, aluminium oxide-magnesium oxide, aluminium oxide-titanium dioxide, silicon dioxide-titanium dioxide and aluminium oxide-boron oxide.
Since the application for that U.S. Pat. No. 4,422,960 there has been a whole series of investigations and inventions which aimed at improving the particle properties on the basis of metal oxides. It will be noted however that satisfactory results have been achieved only to a reasonable extent. There is therefore a need for particulate material which in particular has improved particle stability with at the same time optimised pore size and distribution thereof.
The inventors have now succeeded in developing a particulate material based on metal oxide, which is surprisingly chemically and physically stable under supercritical hydrothermal conditions and in aqueous and protic media.